An apparent new isotope effect in a molecular decomposition and implications for nature

Abstract

The isotopic fractionation resulting from thermal ozone decomposition has been measured. The product O 2 from gas phase thermal decomposition is equally enriched in 17O and 18O with respect to precursor O 3. The effect is not due to O+O 2+M reaction, which is the source of another reported mass-independent isotope effect. Previous experiments have shown that visible light O 3 decomposition produces isotopically light O 2, thus, it appears that the source of the anomalous isotopic fractionation observed in thermal decomposition is the collisional decomposition process. This may then represent a new type of isotope effect not accounted for by theory. The possible consequence for observation in nature is discussed.